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macro_rules! defer { | |
($x:expr) => { | |
let _x = { | |
struct Deferred<F: Fn()>(F); | |
impl<F: Fn()> Drop for Deferred<F> { | |
fn drop(&mut self) { | |
self.0(); | |
} | |
} | |
Deferred(||$x) | |
}; | |
} | |
} | |
use std::ops::{Deref, DerefMut}; | |
pub struct Guard<T, F> where | |
F: FnMut(&mut T) | |
{ | |
__dropfn: F, | |
__value: T, | |
} | |
pub fn guard<T, F>(v: T, dropfn: F) -> Guard<T, F> where | |
F: FnMut(&mut T) | |
{ | |
Guard{__value: v, __dropfn: dropfn} | |
} | |
impl<T, F> Deref for Guard<T, F> where | |
F: FnMut(&mut T) | |
{ | |
type Target = T; | |
fn deref(&self) -> &T | |
{ | |
&self.__value | |
} | |
} | |
impl<T, F> DerefMut for Guard<T, F> where | |
F: FnMut(&mut T) | |
{ | |
fn deref_mut(&mut self) -> &mut T | |
{ | |
&mut self.__value | |
} | |
} | |
impl<T, F> Drop for Guard<T, F> where | |
F: FnMut(&mut T) | |
{ | |
fn drop(&mut self) { | |
(self.__dropfn)(&mut self.__value) | |
} | |
} | |
fn incr(i : &mut i32) {*i += 1;} | |
fn main() { | |
let x = Box::new(5); | |
{ | |
defer!(println!("Defer 1: {:?}",x)); | |
//*x += 1; | |
defer!(println!("Defer 2")); | |
println!("x: {:?}", x); | |
} | |
let mut y = guard(x, |x|println!("y is now: {:?}",x)); | |
**y += 4; | |
println!("y = {:?}", *y); | |
incr(&mut y); | |
let mut z = guard(1, |x|println!("z is now: {:?}",x)); | |
*z += 3; | |
//let b : Box<str> = box *"x"; | |
//let a : _ = &*box b; | |
} | |
/* | |
let _x = { | |
#[derive(Debug)] | |
struct Deferred<F: FnOnce()>(F); | |
impl<F: FnOnce()> Drop for Deferred<F> { | |
fn drop(&mut self) { | |
//println!("Dropping {:?}", $x); | |
replace(&mut self.0, ||{} as F)(); | |
} | |
} | |
Deferred(|| println!("Drop {:?}",x)) | |
}; | |
*/ |
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